Mysql 从两个表中选择多列，其中一个表的一列具有多个where条件，并按两列对它们进行分组并按一进行排序

我有两个表，即“约会”和“技能数据”

预约表的结构如下：

id_ap || ap_meet_date || id_skill || ap_status. 

ap_状态值为完成、确认、取消和错过

而skills_数据表包含两列，即：

id_skill || skill

我想得到每个条件下的预约总数

ap_status = ('complete' and 'confirm'), 
ap_status = 'cancel' and 
ap_status = 'missed' 

GROUP BY id_skill and year and 
order by year DESC

我尝试了这个查询，它只给我一个条件的计数，但我想根据上面提到的GROUPBY和ORDERBY子句得到另外两个条件

如果没有与特定条件匹配的记录（例如：某项技能在2018年错过了零次约会），则应显示零计数的输出值0

是否有人可以建议我使用一个查询，我是否应该实现多个select查询或CASE子句来实现我的预期结果。我在约会表中有很多记录，希望有一种高效的方法来查询我的记录。谢谢大家!

SELECT a.id_skill, YEAR(a.ap_meet_date) As year, s.skill,COUNT(*) as count_comp_conf 
FROM appointment a,skills_data s WHERE a.id_skill=s.id_skill and a.ap_status IN ('complete', 'confirm') 
GROUP BY `id_skill`, `year` 
ORDER BY `YEAR` DESC

我的查询的输出：

 id_skill | year | skill | count_comp_conf 
 -----------------------------------------
 1          2018     A          20        
 2          2018     B          15        
 1          2019     A          10         
 2          2019     B          12 
 3          2019     C          10         

我的预期输出应该如下所示：

 id_skill | year | skill | count_comp_conf | count_cancel | count_missed
 ------------------------------------------------------------------------
 1          2018     A          20             5                 1  
 2          2018     B          15             8                 0  
 1          2019     A          10             4                 1  
 2          2019     B          12             0                 5  
 3          2019     C          10             2                 2

---

当表达式

SELECT a.id_skill, YEAR(a.ap_meet_date) As year, s.skill,
COUNT(case when a.ap_status IN ('complete', 'confirm') then 1 end) as count_comp_conf,
COUNT(case when a.ap_status = 'cancel' then 1 end) as count_cancel,
COUNT(case when a.ap_status = 'missed' then 1 end) as count_missed
FROM appointment a inner join skills_data s on a.id_skill=s.id_skill 
GROUP BY `id_skill`, `year` 
ORDER BY `YEAR` DESC

---

通过下面的查询，您将获得输出

select id_skill ,
year , 
skill , 
count_comp_conf , 
count_cancel , 
count_missed ( select id_skill, year, skill, if ap_status ='Completed' then count_comp_conf+1, elseif ap_status ='cancelled' then count_cancel +1 else count_missed+1
    from appointment a join skills_data s on (a.id_skill = s.id_skill) group by id_skill, year) group by id_skill,year 
    order by year desc;

---

请尝试将if条件与sum一起使用。

或sum（ap_status='cancel'）@草莓，这确实是一个很好的条件，但大多数时候我忘记了这一点：）@fa06它很有效，非常感谢：）但只应删除最后一个条件后的逗号（我的意思是在第四行的count_遗漏之后）.有理由假设答案与OP的问题相关，而无需明确说明。效果很好。谢谢：）在每个IF条件中，1,0意味着什么？在

IF

中，如果条件匹配，则每行返回1或0。然后使用求和函数。谢谢

SELECT a.id_skill, 
   YEAR(a.ap_meet_date) As year, 
   s.skill,
   SUM(IF(a.ap_status IN ('complete', 'confirm'),1,0)) AS count_comp_conf,
   SUM(IF(a.ap_status='cancel',1,0)) AS count_cancel,
   SUM(IF(a.ap_status='missed',1,0)) AS count_missed
FROM appointment a,skills_data s WHERE a.id_skill=s.id_skill 
GROUP BY `id_skill`, `year` 
ORDER BY `YEAR` DESC;